Rotation angle detector, injection system and corresponding operating method

ABSTRACT

A rotation angle detector for detecting the angular position of a shaft, i.e. a camshaft or a camshaft of an internal combustion engine, includes a rotatable detector wheel coupled to the shaft. Markings of a first type are distributed along a periphery of the detector wheel and are detectable by a sensor for determining a relative rational angle. Markings of a second type are also distributed over the periphery of the detector wheel. The markings of the second type are distinguishable from each other for determining an absolute rotational angle of the shaft or for determining selection of a combustion chamber for injection.

[0001] The invention relates to a rotation angle detector for detecting the angular position of a shaft, especially a camshaft or crankshaft of an internal combustion engine comprising several combustion chambers, in accordance with the pre-characterizing clause of claim 1, an injection system according to claim 10 and an operating method for an injection system of this type according to claim 11.

[0002] The injection timing in internal combustion engines having an injection system is conventionally defined as a function of the angular position of the crankshaft. The steps of the injection process are not effected on every revolution for a given combustion chamber in the case of a four-stroke engine, however, so the phase position of the crankshaft must also be known in order to define the injection timing. It is therefore customary also to detect the angular position of the camshaft during the starting process of the internal combustion engine in order to derive therefrom the phase position of the crankshaft.

[0003] The fact that both the angular position of the camshaft and the angular position of the crankshaft have to be detected makes the procedure relatively complex and is thus a disadvantage of the known injection systems.

[0004] The object of the invention is accordingly to determine both the phase position and the angular position of the crankshaft and/or of the camshaft in an injection system in the simplest possible way.

[0005] The invention is, based on a known rotation angle detector for detecting the angular position of a shaft in accordance with the pre-characterizing clause of claim 1, resolved by the characterizing features of claim 1. The problem with respect to the injection system and/or to the corresponding operating method is resolved by the features of claims 10 and/or 11.

[0006] The invention includes the general technical teaching of providing a rotation angle detector that makes it possible to determine both a relative angular position and an absolute angular position and/or a phase position.

[0007] The preferred embodiment thus includes a rotation angle detector having a rotatably mounted detector wheel which is mechanically coupled to the camshaft, the crankshaft or some other shaft, the angular position of which is to be detected. Spread over the periphery of the detector wheel here are numerous markings of a first type that can be detected by a sensor and enable a relative determination of the rotation angle. The markings of the first type are preferably in an evenly spaced arrangement and of a uniform design. The detector wheel may, for example, be realized as a toothed wheel with each tooth constituting a marking of the first type.

[0008] Also spread over the periphery of the detector wheel are several markings of a second type, which markings can be detected by a sensor and can be distinguished from each other so that the absolute rotation angle or phase position of the shaft can be determined. It is thus possible, for example, to arrange a marking of the second type at the start of each quadrant of the detector wheel such that the markings of the second type can be used to determine the quadrant in which the shaft is positioned.

[0009] The markings of the second type in a preferred embodiment consist of two tooth spaces between which a predefined number of teeth is arranged in each case, the markings of the second type differing in respect of the number of teeth between the tooth spaces. The evaluation unit for the rotation angle detector according to the invention thus checks constantly to see whether a tooth space is present, in order then to count the teeth and/or pulses until the next tooth space. The number of teeth between adjacent tooth spaces can then, for example, be allocated to a combustion chamber of an internal combustion engine, which combustion chamber is due for the next injection process.

[0010] The markings of the second type are preferably spread over the periphery of the detector wheel in an evenly spaced arrangement.

[0011] It is furthermore envisaged within the scope of the invention to use the rotation angle detector according to the invention described above to drive an injection system. It is preferable here for one rotation angle detector to be provided for the camshaft and one rotation angle detector to be provided for the crankshaft, the number of pulses/teeth of the detector wheel for the camshaft preferably being an integer multiple of the number of pulses/teeth of the detector wheel for the crankshaft.

[0012] The invention also includes an operating method for an injection system of this type with the rotation angle detector according to the invention.

[0013] It should additionally be mentioned that the rotation angle detector according to the invention can also be used to drive the injection system of multicylinder internal combustion engines having, for example, 6, 8, 10 or 12 cylinders. It is possible here for the synchronization not to be effected directly at the reference mark, but rather to be offset in time from the latter. The synchronization may thus be effected, for example, a predefined number of teeth and/or pulses after the reference mark.

[0014] Other advantageous developments of the invention are characterized in the subclaims or explained in greater detail below together with the description of the preferred embodiment of the invention with reference to the figures.

[0015]FIG. 1 shows an injection system according to the invention having a rotation angle detector according to the invention.

[0016]FIG. 2 shows a pulse diagram of the rotation angle detector according to the invention.

[0017]FIG. 3a shows a detector wheel of the rotation angle detector according to the invention.

[0018]FIG. 3b shows an alternative embodiment of a detector wheel.

[0019] The schematic block diagram presented in FIG. 1 shows an injection system 1 for driving four injectors INJ1-INJ4, the injection system 1 being connected to a rotation angle detector 2 for the crankshaft and a rotation angle detector 3 for the camshaft.

[0020] The rotation angle detector 2 for the crankshaft is of largely conventional design and is not therefore described in any greater detail below. The pulse train KW generated by the rotation angle detector 2 is, however, reproduced in the pulse diagram presented in FIG. 2. It can be seen from the pulse diagram that the rotation angle detector 2 for the crankshaft generates a continuous pulse train that enables only a relative determination of the rotation angle and that the phase position of the crankshaft is not apparent in the pulse train generated by the rotation angle detector 2.

[0021] The rotation angle detector 3 for the camshaft is, in contrast, of a special design as described below. The rotation angle detector 3 has a detector wheel realized as a toothed wheel and presented in FIG. 3a having a tooth pitch of 60 teeth, each tooth constituting a marking 4 of the first type, which marking enables a relative determination of the rotation angle.

[0022] The detector wheel of the rotation angle detector 3 has in addition four markings 5 of a second type, each of which comprises two tooth spaces 6.1, 6.2, each consisting of two teeth, between which a predefined number of teeth is arranged in each case. The number of teeth arranged between the tooth spaces 6.1, 6.2 here determines the number of the combustion chamber of the internal combustion engine due for an injection process.

[0023] The evaluation device for the rotation angle detector 3 arranged in the injection system 1 therefore counts the number of pulses and/or teeth 4 between one detected tooth space 6.1, 6.2 and the next tooth space. If the value determined lies between one and the number of combustion chambers in the internal combustion engine, the next pulse edge to occur is used as reference mark α_(REF) for the combustion chamber number previously determined. If, on the other hand, the value of pulses determined in the counting process between the tooth spaces 6.1, 6.2 is greater than the number of combustion chambers, the marking is not a marking 5 of the second type and consequently no reference mark is generated.

[0024] The markings 5 of the second type described above advantageously enable a cylinder selection and/or a synchronization by means of the camshaft signal such that operation of the injection system remains possible even after a failure of the rotation angle detector 2 for the crankshaft.

[0025]FIG. 3b shows an alternative embodiment of a detector wheel for the rotation angle detector 3 of the camshaft that largely coincides with the embodiment described above and shown in FIG. 3a, as a result of which the same reference numbers are used below and reference is made to the description above to avoid repetitions.

[0026] The special feature of the detector wheel according to FIG. 3b is that markings in the form of radial lines that can be sampled by an optical sensor are provided instead of teeth. Each of the individual radial lines here constitutes a marking 4 of the first type. Each of the markings 5 of the second type comprises two gaps 6.1, 6.2 with an angular extent of two lines between which a predefined number of radial lines are arranged. The number of radial lines between the two gaps 6.1, 6.2 indicates the number of the combustion chamber concerned.

[0027] The invention is not limited to the preferred embodiments described above. It is rather the case that there are a large number of conceivable variants and modifications that make use of the inventive idea and consequently also fall within the scope of protection. 

1. Rotation angle detector for detecting the angular position of a shaft, especially a camshaft or crankshaft of an internal combustion engine comprising several combustion chambers, having a rotatably mounted detector wheel which is mechanically coupled to the shaft, there being spread over the periphery of the detector wheel numerous markings (4) of a first type that can be detected by a sensor and enable a relative determination of the rotation angle, characterized in that several markings (5) of a second type are spread over the periphery of the detector wheel, which markings can be detected by a sensor and can be distinguished from each other in order to determine the absolute rotation angle or phase position of the shaft or to enable a combustion chamber to be selected for fuel injection.
 2. Rotation angle detector according to claim 1, characterized in that the markings (5) of the second type can be distinguished from each other in respect of their angular extent.
 3. Rotation angle detector according to claim 1 or 2, characterized in that the markings (5) of the first type are in an evenly spaced arrangement at least in sub-sections of the detector wheel.
 4. Rotation angle detector according to one or more of the preceding claims, characterized in that the number of markings (5) of the second type equals the number of combustion chambers in the internal combustion engine in order that each marking (5) of the second type can be allocated a combustion chamber of the internal combustion engine.
 5. Rotation angle detector according to one or more of the preceding claims, characterized in that the detector wheel is realized as a toothed wheel, the markings (4) of the first type and/or the markings (5) of the second type being teeth.
 6. Rotation angle detector according to claim 5, characterized in that the markings (5) of the second type consist of two tooth spaces (6.1, 6.2) between which a predefined number of teeth is arranged in each case, it being possible to distinguish the markings (5) of the second type from each other in respect of the number of teeth between the tooth spaces (6.1, 6.2).
 7. Rotation angle detector according to claim 6, characterized in that the tooth spaces (6.1, 6.2) in each case have an angular extent of at least two teeth (4).
 8. Rotation angle detector according to one or more of the preceding claims, characterized in that the markings (5) of the second type are spread over the periphery of the detector wheel in an evenly spaced arrangement.
 9. Rotation angle detector according to one or more of the preceding claims, characterized in that the detector wheel is mechanically coupled to a camshaft [of] an internal combustion engine, while a further detector wheel is mechanically coupled to the crankshaft of the internal combustion engine, the number of markings (5) of the first type on the detector wheel for the camshaft being an integer multiple of the number of markings on the detector wheel for the crankshaft.
 10. Injection system for an internal combustion engine having a rotation angle detector according to one of the preceding claims for determining the injection timing for the combustion chambers of the internal combustion engine.
 11. Operating method for an injection system of an internal combustion engine having a rotation angle detector according to one of claims 1 to 8 with the following steps: detection of the markings (4) of the first type while the shaft is rotating, definition of the injection timing by means of the markings (4) of the first type, detection of the markings (5) of the second type and the corresponding angular position of the shaft, selection of a combustion chamber of the internal combustion engine by means of the respective marking (5) of the second type, injection of fuel into the combustion chamber selected by means of the markings (5) of the second type with the injection timing defined by means of the markings (4) of the first type.
 12. Operating method according to claim 11, characterized in that the angular extent of the markings (5) of the second type is determined, the selection of a combustion chamber being made by means of the angular extent of the markings (5) of the second type.
 13. Operating method according to claim 12, characterized in that the number of markings (4) of the first type between one space (6.1, 6.2) in the markings (4) of the first type and the next space (6.1, 6.2) in the markings (4) of the first type is counted, the selection of a combustion chamber for injection being made by means of the number of markings (4) of the first type between the two spaces (6.1, 6.2).
 14. Operating method according to claim 13, characterized in that the number of markings (4) of the first type between two spaces (6.1, 6.2) is compared with the number of combustion chambers, a combustion chamber only being selected if the number of markings (4) of the first type between the two spaces (6.1, 6.2) is smaller than or equal to the number of combustion chambers in the internal combustion engine.
 15. Operating method according to claim 13 or 14, characterized in that after two successive spaces (6.1, 6.2) in the markings (4) of the first type, the next marking (4) of the first type is adopted as reference angle (α_(REF)) for the selection of a combustion chamber. 